[Auth] Fix popup opening location

[sam-gc]

Also fix/augment the tests which, embarrassingly, were actually testing for the wrong behavior...

Fixes #5275

[changeset-bot]

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Latest commit: e27a781

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[github-actions]

Changeset File Check ⚠️

• Changeset formatting error in following file:

  Package "firebase-compat-typings-test" must depend on the current version of "firebase-exp": "9.0.0-beta.8" vs "file:../../packages-exp/firebase-exp"
  Package "firebase-compat-typings-test" must depend on the current version of "firebase-exp": "9.0.0-beta.8" vs "file:../../packages-exp/firebase-exp"
  Package "firebase-compat-typings-test" must depend on the current version of "firebase-exp": "9.0.0-beta.8" vs "file:../../packages-exp/firebase-exp"
  Some packages have been changed but no changesets were found. Run `changeset add` to resolve this error.
  If this change doesn't need a release, run `changeset add --empty`.
  

[google-oss-bot]

Binary Size Report

Affected SDKs

No changes between base commit (a69220b) and head commit (62ee189).

Test Logs

• Base (a69220b5): https://github.com/firebase/firebase-js-sdk/actions/runs/1121766378
• Head (62ee1892): https://github.com/firebase/firebase-js-sdk/actions/runs/1121950815

[google-oss-bot]

Size Analysis Report

Affected Products

No changes between base commit (a69220b) and head commit (62ee189).

Test Logs

• Base (a69220b): https://github.com/firebase/firebase-js-sdk/actions/runs/1121766378
• Head (62ee189): https://github.com/firebase/firebase-js-sdk/actions/runs/1121950815